Rebase.Data.Eq

Equality of constructors

Note that due to the presence of NaN, Double's Eq instance does not satisfy reflexivity.

>>> 0/0 == (0/0 :: Double)False

Also note that Double's Eq instance does not satisfy substitutivity:

>>> 0 == (-0 :: Double)True>>> recip 0 == recip (-0 :: Double)False

Note that due to the presence of NaN, Float's Eq instance does not satisfy reflexivity.

>>> 0/0 == (0/0 :: Float)False

Also note that Float's Eq instance does not satisfy extensionality:

>>> 0 == (-0 :: Float)True>>> recip 0 == recip (-0 :: Float)False

Byte equality of the internal representation.

Byte equality of the internal representation.

Scientific numbers can be safely compared for equality. No magnitude 10^e is calculated so there's no risk of a blowup in space or time when comparing scientific numbers coming from untrusted sources.

Pointer equality.

Compares the underlying pointers.

Uses precomputed hash to detect inequality faster

Note that, in the presence of hash collisions, equal HashSets may behave differently, i.e. extensionality may be violated:

>>> data D = A | B deriving (Eq, Show)>>> instance Hashable D where hashWithSalt salt _d = salt

>>> x = fromList [A, B]>>> y = fromList [B, A]

>>> x == yTrue>>> toList x[A,B]>>> toList y[B,A]

In general, the lack of extensionality can be observed with any function that depends on the key ordering, such as folds and traversals.

Pointer equality.

Note that, in the presence of hash collisions, equal HashMaps may behave differently, i.e. extensionality may be violated:

>>> data D = A | B deriving (Eq, Show)>>> instance Hashable D where hashWithSalt salt _d = salt

>>> x = fromList [(A,1), (B,2)]>>> y = fromList [(B,2), (A,1)]

>>> x == yTrue>>> toList x[(A,1),(B,2)]>>> toList y[(B,2),(A,1)]

In general, the lack of extensionality can be observed with any function that depends on the key ordering, such as folds and traversals.